package com.cainli.image.gif;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.lang.ref.SoftReference;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Locale;

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;

/**
 * Gif decoder 提供同步和异步处理
 * 
 * {@link GifDrawable}  异步例子，
 * {@link SyncGifDrawable} 同步例子
 * 
 * @author cainli   2013-2-1  下午2:17:26
 *
 */
public class GifDecoder {

  /**
   * File read status: No errors.
   */
  public static final int STATUS_OK = 0;

  /**
   * File read status: Error decoding file (may be partially decoded)
   */
  public static final int STATUS_FORMAT_ERROR = 1;

  /**
   * File read status: Unable to open source.
   */
  public static final int STATUS_OPEN_ERROR = 2;
  
  /**
   * File read status: Unable to close source.
   */
  public static final int STATUS_CLOSE_ERROR = 3;
  
  public static final int STATUS_URL_ERROR = 4;
  
  public static final int STATUS_FILE_NOT_FOUND_ERROR = 5;
  
  public static final int STATUS_IO_ERROR = 6;

  protected int status;

  protected int width; // full image width

  protected int height; // full image height

  protected boolean gctFlag; // global color table used

  protected int gctSize; // size of global color table

  protected int loopCount = 1; // iterations; 0 = repeat forever

  protected int[] gct; // global color table

  protected int[] lct; // local color table

  protected int[] act; // active color table

  protected int bgIndex; // background color index

  protected int bgColor; // background color

  protected int lastBgColor; // previous bg color

  protected int pixelAspect; // pixel aspect ratio

  protected boolean lctFlag; // local color table flag

  protected boolean interlace; // interlace flag

  protected int lctSize; // local color table size

  protected int ix, iy, iw, ih; // current image rectangle

  protected Rect lastRect; // last image rect

  protected Bitmap image; // current frame

  protected Bitmap lastImage; // previous frame

  protected ArrayList<Paint> background = new ArrayList<Paint>();

  protected byte[] block = new byte[256]; // current data block

  protected int blockSize = 0; // block size

  // last graphic control extension info
  protected int dispose = 0;

  // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
  protected int lastDispose = 0;

  protected boolean transparency = false; // use transparent color

  protected int delay = 0; // delay in milliseconds

  protected int transIndex; // transparent color index

  protected static final int MaxStackSize = 4096;

  // max decoder pixel stack size

  // LZW decoder working arrays
  protected short[] prefix;

  protected byte[] suffix;

  protected byte[] pixelStack;

  protected byte[] pixels;

  protected ArrayList<GifFrame> frames; // frames read from current file

  protected int frameCount;
  
  private DecoderCallBack callBack;
  
  private RandomAccessFile raf;
  
  private long currentPostion = -1;

	/**
	 * decoder 回调函数
	 * 
	 * @author cainli 2013-1-31 下午4:21:18
	 * 
	 */
	public static interface DecoderCallBack {

		public void onGetOneFrame(GifFrame gifFrame, int index, long nextFrameTime);

		public void onGetGifSize(int width, int height);
	}
  
  public static class GifFrame {
    public GifFrame(Bitmap im, int del) {
      image = new SoftReference<Bitmap>(im);
      delay = del;
    }
    public SoftReference<Bitmap>  image =  new SoftReference<Bitmap>(null);

    public int delay;
  }

  public void setCallBack(DecoderCallBack callBack) {
	this.callBack = callBack;
}

/**
   * Gets display duration for specified frame.
   * 
   * @param n
   *          int index of frame
   * @return delay in milliseconds
   */
  public int getDelay(int n) {
    //
    delay = -1;
    if ((n >= 0) && (n < frameCount)) {
      delay = ((GifFrame) frames.get(n)).delay;
    }
    return delay;
  }

  /**
   * Gets the number of frames read from file.
   * 
   * @return frame count
   */
  public int getFrameCount() {
    return frameCount;
  }
  
  public  ArrayList<GifFrame> getFrames(){
	  return frames;
  }
  
  public Paint getBackground(int ix){
	  return null;
  }

  /**
   * Gets the first (or only) image read.
   * 
   * @return Bitmap containing first frame, or null if none.
   */
  public Bitmap getImage() {
    return getFrame(0);
  }

  /**
   * Gets the "Netscape" iteration count, if any. A count of 0 means repeat
   * indefinitiely.
   * 
   * @return iteration count if one was specified, else 1.
   */
  public int getLoopCount() {
    return loopCount;
  }

  /**
   * Creates new frame image from current data (and previous frames as specified
   * by their disposition codes).
   */
  protected void setPixels() throws Exception {
    // expose destination image's pixels as int array
    int[] dest = new int[image.getWidth()*image.getHeight()];
    // fill in starting image contents based on last image's dispose code
    if (lastDispose > 0) {
      if (lastDispose == 3) {
        // use image before last
        int n = frameCount - 2;
        if (n > 0) {
          lastImage = getFrame(n - 1);
        } else {
          lastImage = null;
        }
      }

      if (lastImage != null) {
          Canvas cv = new Canvas(image);
          cv.drawBitmap(lastImage, 0, 0, null);// copy pixels
        if (lastDispose == 2) {
          // fill last image rect area with background color
          Paint bkp = new Paint(Paint.FILTER_BITMAP_FLAG);
    	  bkp.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
    	  bkp.setStyle(Style.FILL);
          if (transparency) {
        	  bkp.setColor(0x00000000);// assume background is transparent
          } else {
        	  bkp.setColor(lastBgColor);// use given background color
          }
          cv.drawRect(lastRect, bkp); // replace area
        }
        image.getPixels(dest, 0, image.getWidth(), 0, 0, image.getWidth(), image.getHeight());
      }
    }

    // copy each source line to the appropriate place in the destination
    int pass = 1;
    int inc = 8;
    int iline = 0;
    for (int i = 0; i < ih; i++) {
      int line = i;
      if (interlace) {
        if (iline >= ih) {
          pass++;
          switch (pass) {
          case 2:
            iline = 4;
            break;
          case 3:
            iline = 2;
            inc = 4;
            break;
          case 4:
            iline = 1;
            inc = 2;
          }
        }
        line = iline;
        iline += inc;
      }
      line += iy;
      if (line < height) {
        int k = line * width;
        int dx = k + ix; // start of line in dest
        int dlim = dx + iw; // end of dest line
        if ((k + width) < dlim) {
          dlim = k + width; // past dest edge
        }
        int sx = i * iw; // start of line in source
        while (dx < dlim) {
          // map color and insert in destination
          int index = ((int) pixels[sx++]) & 0xff;
          int c = act[index];
          if (c != 0) {
            dest[dx] = c;
          }
          dx++;
        }
      }
    }
    image.setPixels(dest, 0, image.getWidth(), 0, 0, image.getWidth(), image.getHeight());
  }

  /**
   * Gets the image contents of frame n.
   * 
   * @return Bitmap representation of frame, or null if n is invalid.
   */
  public Bitmap getFrame(int n) {
	  Bitmap im = null;
    if ((n >= 0) && (n < frameCount)) {
    	im = frames.get(n).image.get();
    }
    return im;
  }

  /**
   * Gets image size.
   * 
   * @return GIF image dimensions
   */
  public Dimension getFrameSize() {
    return new Dimension(width, height);
  }
  
  public class Dimension{
	  public int width;
	  public int height;
	  Dimension(int w, int h){
		  width = w;
		  height = h;
	  }
  }
  
 
 /**
  * 读取图片唯一接口
  * @param name
  * @param onlyReadHeader  true 只读文件头 ，false 全部读取，如果已经读过头，则跳过，直接读内容
  * @return
  */
public  int read(String name, boolean onlyReadHeader){
		init();
		try {
			File f;
			name = name.trim().toLowerCase(Locale.getDefault());
			if ((name.indexOf("file:") >= 0) || (name.indexOf(":/") > 0)) {
				URL url = new URL(name);
				f = new File(url.getPath());
			} else {
				f = new File(name);
			}
			raf = new RandomAccessFile(f, "r");
			if (raf != null) {
				if (onlyReadHeader) {
					readHeader();
				} else {
					readFrames();
				}
			} else {
				status = STATUS_OPEN_ERROR;
			}
		} catch (FileNotFoundException e) {
			status = STATUS_FILE_NOT_FOUND_ERROR;
		} catch (MalformedURLException e) {
			status = STATUS_URL_ERROR;
		} catch (IOException e) {
			status = STATUS_IO_ERROR;
		} finally {
			try {
				raf.close();
			} catch (IOException e) {
				status = STATUS_CLOSE_ERROR;
			}
		}
		return status;
}
	

  /**
   * 读取内容
   * @return
   */
  private int readFrames(){
		if (raf != null) {
			try {
				if(currentPostion==-1){ //没有调用读header方法，
					readHeader();
				}else{
					raf.seek(currentPostion);
				}
				readContents();
			} catch (IOException e) {
				status = STATUS_OPEN_ERROR;
			} catch (Exception e) {
				status = STATUS_OPEN_ERROR;
			}
			try {
				raf.close();
			} catch (IOException e) {
			}
		}
		if (frameCount < 0) {
			status = STATUS_FORMAT_ERROR;
		}
		return status;
  }
  

  
  /**
   * Decodes LZW image data into pixel array. Adapted from John Cristy's
   * ImageMagick.
   */
  protected void decodeImageData() {
    int NullCode = -1;
    int npix = iw * ih;
    int available, clear, code_mask, code_size, end_of_information, in_code, old_code, bits, code, count, i, datum, data_size, first, top, bi, pi;

    if ((pixels == null) || (pixels.length < npix)) {
      pixels = new byte[npix]; // allocate new pixel array
    }
    if (prefix == null)
      prefix = new short[MaxStackSize];
    if (suffix == null)
      suffix = new byte[MaxStackSize];
    if (pixelStack == null)
      pixelStack = new byte[MaxStackSize + 1];

    // Initialize GIF data stream decoder.

    data_size = read();
    clear = 1 << data_size;
    end_of_information = clear + 1;
    available = clear + 2;
    old_code = NullCode;
    code_size = data_size + 1;
    code_mask = (1 << code_size) - 1;
    for (code = 0; code < clear; code++) {
      prefix[code] = 0;
      suffix[code] = (byte) code;
    }

    // Decode GIF pixel stream.

    datum = bits = count = first = top = pi = bi = 0;

    for (i = 0; i < npix;) {
      if (top == 0) {
        if (bits < code_size) {
          // Load bytes until there are enough bits for a code.
          if (count == 0) {
            // Read a new data block.
            count = readBlock();
            if (count <= 0)
              break;
            bi = 0;
          }
          datum += (((int) block[bi]) & 0xff) << bits;
          bits += 8;
          bi++;
          count--;
          continue;
        }

        // Get the next code.

        code = datum & code_mask;
        datum >>= code_size;
        bits -= code_size;

        // Interpret the code

        if ((code > available) || (code == end_of_information))
          break;
        if (code == clear) {
          // Reset decoder.
          code_size = data_size + 1;
          code_mask = (1 << code_size) - 1;
          available = clear + 2;
          old_code = NullCode;
          continue;
        }
        if (old_code == NullCode) {
          pixelStack[top++] = suffix[code];
          old_code = code;
          first = code;
          continue;
        }
        in_code = code;
        if (code == available) {
          pixelStack[top++] = (byte) first;
          code = old_code;
        }
        while (code > clear) {
          pixelStack[top++] = suffix[code];
          code = prefix[code];
        }
        first = ((int) suffix[code]) & 0xff;

        // Add a new string to the string table,

        if (available >= MaxStackSize)
          break;
        pixelStack[top++] = (byte) first;
        prefix[available] = (short) old_code;
        suffix[available] = (byte) first;
        available++;
        if (((available & code_mask) == 0) && (available < MaxStackSize)) {
          code_size++;
          code_mask += available;
        }
        old_code = in_code;
      }

      // Pop a pixel off the pixel stack.

      top--;
      pixels[pi++] = pixelStack[top];
      i++;
    }

    for (i = pi; i < npix; i++) {
      pixels[i] = 0; // clear missing pixels
    }

  }

  /**
   * Returns true if an error was encountered during reading/decoding
   */
  protected boolean err() {
    return status != STATUS_OK;
  }

  /**
   * Initializes or re-initializes reader
   */
  protected void init() {
    status = STATUS_OK;
    frameCount = 0;
    frames = new ArrayList<GifFrame>();
    gct = null;
    lct = null;
    currentPostion = -1;
  }

  /**
   * Reads a single byte from the input stream.
   */
  protected int read() {
    int curByte = 0;
    try {
      curByte = raf.read();
    } catch (IOException e) {
      status = STATUS_FORMAT_ERROR;
    }
    return curByte;
  }
  
  /**
   * 获取当前位置
   */
  protected void readPostion() {
    try {
      currentPostion  = raf.getFilePointer();
    } catch (IOException e) {
      status = STATUS_FORMAT_ERROR;
    }
  }

  /**
   * Reads next variable length block from input.
   * 
   * @return number of bytes stored in "buffer"
   */
  protected int readBlock() {
    blockSize = read();
    int n = 0;
    if (blockSize > 0) {
      try {
        int count = 0;
        while (n < blockSize) {
          count = raf.read(block, n, blockSize - n);
          if (count == -1)
            break;
          n += count;
        }
      } catch (IOException e) {
      }

      if (n < blockSize) {
        status = STATUS_FORMAT_ERROR;
      }
    }
    return n;
  }

  /**
   * Reads color table as 256 RGB integer values
   * 
   * @param ncolors
   *          int number of colors to read
   * @return int array containing 256 colors (packed ARGB with full alpha)
   */
  protected int[] readColorTable(int ncolors) {
    int nbytes = 3 * ncolors;
    int[] tab = null;
    byte[] c = new byte[nbytes];
    int n = 0;
    try {
      n = raf.read(c);
    } catch (IOException e) {
    }
    if (n < nbytes) {
      status = STATUS_FORMAT_ERROR;
    } else {
      tab = new int[256]; // max size to avoid bounds checks
      int i = 0;
      int j = 0;
      while (i < ncolors) {
        int r = ((int) c[j++]) & 0xff;
        int g = ((int) c[j++]) & 0xff;
        int b = ((int) c[j++]) & 0xff;
        tab[i++] = 0xff000000 | (r << 16) | (g << 8) | b;
      }
    }
    return tab;
  }

  /**
   * Main file parser. Reads GIF content blocks.
   */
  protected void readContents() throws Exception {
    // read GIF file content blocks
    boolean done = false;
    while (!(done || err())) {
      int code = read();
      switch (code) {

      case 0x2C: // image separator
    	  try {
    		  if(!readImage()){
        		  return;
        	  }
    		} catch (OutOfMemoryError error) {
    			/*
    			 * 内存溢出了··就不继续解码了
    			 * 如果继续创建bitmap 可能继续OOM，
    			 * 如果跳下一帧 又会出现gif跳帧，所以直接结束解码
    			 */
    		}
        break;

      case 0x21: // extension
        code = read();
        switch (code) {
        case 0xf9: // graphics control extension
          readGraphicControlExt();
          break;

        case 0xff: // application extension
          readBlock();
          String app = "";
          for (int i = 0; i < 11; i++) {
            app += (char) block[i];
          }
          if (app.equals("NETSCAPE2.0")) {
            readNetscapeExt();
          } else
            skip(); // don't care
          break;

        default: // uninteresting extension
          skip();
        }
        break;

      case 0x3b: // terminator
        done = true;
        break;

      case 0x00: // bad byte, but keep going and see what happens
        break;

      default:
        status = STATUS_FORMAT_ERROR;
      }
    }
  }

  /**
   * Reads Graphics Control Extension values
   */
  protected void readGraphicControlExt() {
    read(); // block size
    int packed = read(); // packed fields
    dispose = (packed & 0x1c) >> 2; // disposal method
    //if (dispose == 0) {
    //  dispose = 1; // elect to keep old image if discretionary
    //}
    transparency = (packed & 1) != 0;
    delay = readShort() * 10; // delay in milliseconds
    transIndex = read(); // transparent color index
    read(); // block terminator
  }

  /**
   * Reads GIF file header information.
 * @throws IOException 
   */
  protected void readHeader() throws IOException {
    String id = "";
    for (int i = 0; i < 6; i++) {
      id += (char) read();
    }
    if (!id.startsWith("GIF")) {
      status = STATUS_FORMAT_ERROR;
      return;
    }

    readLSD();
    if (gctFlag && !err()) {
      gct = readColorTable(gctSize);
      bgColor = gct[bgIndex];
    }
    readPostion();
  }

  /**
   *  Reads next frame image
   * @return true 继续解码，false 停止解码
   * @throws Exception
   */
  protected boolean readImage() throws Exception {
	long nextFrameTime = android.os.SystemClock.uptimeMillis() + getDelay();
    ix = readShort(); // (sub)image position & size
    iy = readShort();
    iw = readShort();
    ih = readShort();

    int packed = read();
    lctFlag = (packed & 0x80) != 0; // 1 - local color table flag
    interlace = (packed & 0x40) != 0; // 2 - interlace flag
    // 3 - sort flag
    // 4-5 - reserved
    lctSize = 2 << (packed & 7); // 6-8 - local color table size

    if (lctFlag) {
      lct = readColorTable(lctSize); // read table
      act = lct; // make local table active
    } else {
      act = gct; // make global table active
      if (bgIndex == transIndex)
        bgColor = 0;
    }
    int save = 0;
    if (transparency) {
      save = act[transIndex];
      act[transIndex] = 0; // set transparent color if specified
    }

    if (act == null) {
      status = STATUS_FORMAT_ERROR; // no color table defined
    }

    if (err())
      return false;

    decodeImageData(); // decode pixel data
    skip();

    if (err())
      return false;

    frameCount++;

   	// create new image to receive frame data
	image = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_4444);

    setPixels(); // transfer pixel data to image

    GifFrame gifFrame = new GifFrame(image,  getDelay());
    if(callBack!=null){
    	callBack.onGetOneFrame(gifFrame, frameCount,nextFrameTime);
    }
    frames.add(gifFrame); // add image to frame list
    currrentFrame = gifFrame;
    if (transparency) {
      act[transIndex] = save;
    }
    resetFrame();
    
	return true;

  }
  
  /**
   *限制最小的延时
   * @return
   */
  public int getDelay(){
	return   delay < 100 ? 100 : delay;
  }

  /**
   * Reads Logical Screen Descriptor
   */
  protected void readLSD() {

    // logical screen size
    width = readShort();
    height = readShort();
    if(callBack!=null){
    	callBack.onGetGifSize(width,height);
    }

    // packed fields
    int packed = read();
    gctFlag = (packed & 0x80) != 0; // 1 : global color table flag
    // 2-4 : color resolution
    // 5 : gct sort flag
    gctSize = 2 << (packed & 7); // 6-8 : gct size

    bgIndex = read(); // background color index
    pixelAspect = read(); // pixel aspect ratio
  }

  /**
   * Reads Netscape extenstion to obtain iteration count
   */
  protected void readNetscapeExt() {
    do {
      readBlock();
      if (block[0] == 1) {
        // loop count sub-block
        int b1 = ((int) block[1]) & 0xff;
        int b2 = ((int) block[2]) & 0xff;
        loopCount = (b2 << 8) | b1;
      }
    } while ((blockSize > 0) && !err());
  }

  /**
   * Reads next 16-bit value, LSB first
   */
  protected int readShort() {
    // read 16-bit value, LSB first
    return read() | (read() << 8);
  }

  /**
   * Resets frame state for reading next image.
   */
  protected void resetFrame() {
    lastDispose = dispose;
    lastRect = new Rect(ix, iy, iw+ix, ih+iy);
    lastImage = image;
    lastBgColor = bgColor;
    //dispose = 0;
    //transparency = false;
    //delay = 0;
    lct = null;
  }
  

  /**
   * Skips variable length blocks up to and including next zero length block.
   */
  protected void skip() {
    do {
      readBlock();
    } while ((blockSize > 0) && !err());
  }

	/*
	 * 以下都是为了提供同步的方法调用
	 */
	private String path;
	private File f;
	private long currentFramePosition;
	private GifFrame currrentFrame;

	/**
	 * @param path
	 * @throws MalformedURLException
	 * @throws FileNotFoundException
	 */
	public void setPath(String path) throws FileNotFoundException {
		this.path = path;
		f = new File(path);
		if (f != null && f.exists()) {
			raf = new RandomAccessFile(f, "r");
		}
		init();
	}

	public GifFrame nextFrame() throws Exception {
		if (raf == null) {
			throw new Exception(
					" you should call setPath(String path) firsttime   befor call nextFrame()!!!");
		}
		if (frameCount == 0) {
			readHeader();
		}
		readContentsSync();
		if (currrentFrame == null) {
			if (raf != null) {
				try {
					raf.close();
				} catch (Exception e) {
				}
			}
		}
		return currrentFrame;
	}
	
	public void close(){
		if(raf!=null){
			try{
				raf.close();
			}catch (Exception e) {
			}
		}
	}

	/**
	 * 阻塞式读取
	 * 
	 * @throws Exception
	 */
	private void readContentsSync() throws Exception{
		// read GIF file content blocks
		boolean done = false;
		while (!(done || err())) {
			int code = read();
			switch (code) {
			case 0x2C: // image separator
				readImage();
				currentFramePosition = raf.getFilePointer();
				return;
			case 0x21: // extension
				code = read();
				switch (code) {
				case 0xf9: // graphics control extension
					readGraphicControlExt();
					break;

				case 0xff: // application extension
					readBlock();
					String app = "";
					for (int i = 0; i < 11; i++) {
						app += (char) block[i];
					}
					if (app.equals("NETSCAPE2.0")) {
						readNetscapeExt();
					} else
						skip(); // don't care
					break;

				default: // uninteresting extension
					skip();
				}
				break;

			case 0x3b: // terminator
				done = true;
				currrentFrame = null;
				break;

			case 0x00: // bad byte, but keep going and see what happens
				break;

			default:
				status = STATUS_FORMAT_ERROR;
			}
		}
	}

}